Pagination patterns in Supabase

Introduction

Pagination helps show data in small parts instead of all at once. This makes apps faster and easier to use.

Showing a list of users in a dashboard with many entries.

Loading posts on a blog page without slowing down the site.

Displaying search results in small chunks for better reading.

Fetching product items in an online store page by page.

Syntax

Supabase

const { data, error } = await supabase
  .from('table_name')
  .select('*')
  .range(fromIndex, toIndex);

.range(from, to) fetches rows starting at from index up to to index.

Indexes start at 0, so .range(0, 9) gets the first 10 rows.

Examples

Gets the first 10 products from the 'products' table.

Supabase

const { data, error } = await supabase
  .from('products')
  .select('*')
  .range(0, 9);

Gets the second page of users, rows 11 to 20.

Supabase

const { data, error } = await supabase
  .from('users')
  .select('*')
  .range(10, 19);

Fetches page 3 of orders with 5 items per page.

Supabase

const pageSize = 5;
const page = 3;
const from = (page - 1) * pageSize;
const to = from + pageSize - 1;

const { data, error } = await supabase
  .from('orders')
  .select('*')
  .range(from, to);

Sample Program

This program connects to Supabase, defines a function to get a page of data from any table, and fetches the second page of users with 3 users per page. It prints the users to the console.

Supabase

import { createClient } from '@supabase/supabase-js';

const supabaseUrl = 'https://xyzcompany.supabase.co';
const supabaseKey = 'public-anonymous-key';
const supabase = createClient(supabaseUrl, supabaseKey);

async function fetchPage(table, page, pageSize) {
  const from = (page - 1) * pageSize;
  const to = from + pageSize - 1;
  const { data, error } = await supabase
    .from(table)
    .select('*')
    .range(from, to);
  if (error) {
    console.error('Error fetching data:', error.message);
    return [];
  }
  return data;
}

(async () => {
  const page = 2;
  const pageSize = 3;
  const users = await fetchPage('users', page, pageSize);
  console.log('Users page', page, ':', users);
})();

Important Notes

Always check for errors after fetching data to handle problems gracefully.

Use consistent page sizes to keep user experience smooth.

Pagination reduces load and speeds up your app by loading only needed data.

Summary

Pagination splits large data into smaller, easy-to-handle parts.

Use .range(from, to) in Supabase to get specific rows.

Calculate indexes carefully to fetch the right page of data.

Practice

1. What does the .range(from, to) method do in Supabase pagination?

easy

A. It sorts the rows between from and to indexes.

B. It limits the total number of rows returned to to.

C. It fetches rows starting from index from up to index to inclusive.

D. It skips the first from rows and returns the rest.

Solution

1. Step 1: Understand the purpose of .range(from, to)

   This method is used to select a slice of rows by index, starting at from and ending at to, inclusive.

2. Step 2: Compare options with this behavior

   Only the option stating 'It fetches rows starting from index from up to index to inclusive.' correctly describes the slicing behavior. The other options describe sorting, limiting, or skipping incorrectly.

3. Final Answer:

   It fetches rows starting from index from up to index to inclusive. -> Option C

4. Quick Check:

   .range(from, to) = fetch rows from-to inclusive [OK]

Hint: Remember range is inclusive from start to end index [OK]

Common Mistakes:

• Thinking to is exclusive
• Confusing .range with .limit
• Assuming it skips rows instead of slicing

2. Which of the following is the correct syntax to fetch page 3 with 10 items per page using Supabase's .range()?

easy

A. .range(20, 29)

B. .range(30, 39)

C. .range(21, 30)

D. .range(10, 19)

Solution

1. Step 1: Calculate start and end indexes for page 3

   Page 3 means items 21 to 30 (1-based). Since .range() uses 0-based indexes, start = (3-1)*10 = 20, end = 20 + 9 = 29.

2. Step 2: Match calculated range with options

   .range(20, 29) matches the correct 0-based slice for page 3.

3. Final Answer:

   .range(20, 29) -> Option A

4. Quick Check:

   Page 3 with 10 items = indexes 20 to 29 [OK]

Hint: Page N with size S starts at (N-1)*S [OK]

Common Mistakes:

• Using 1-based indexes directly
• Off-by-one errors in start or end
• Confusing page number with item count

3. Given this Supabase query:

const page = 2;
const pageSize = 5;
const { data } = await supabase
  .from('products')
  .select('*')
  .range((page - 1) * pageSize, page * pageSize - 1);

How many rows will data contain?

medium

A. 6

B. 10

C. 4

D. 5

Solution

1. Step 1: Calculate the range indexes

   For page 2 and pageSize 5, start = (2-1)*5 = 5, end = 2*5 - 1 = 9.

2. Step 2: Determine number of rows fetched

   Indexes 5 to 9 inclusive means 5 rows (5,6,7,8,9).

3. Final Answer:

   5 -> Option D

4. Quick Check:

   Range length = end - start + 1 = 5 [OK]

Hint: Count rows as end - start + 1 [OK]

Common Mistakes:

• Counting end index as exclusive
• Miscalculating start or end
• Assuming pageSize is ignored

4. You wrote this code to fetch page 1 with 10 items per page:

const page = 1;
const pageSize = 10;
const { data } = await supabase
  .from('orders')
  .select('*')
  .range(page * pageSize, (page + 1) * pageSize - 1);

Why does this return no rows?

medium

A. Because .range() requires the start index to be less than the end index.

B. Because the range starts at 10 instead of 0, skipping the first page.

C. Because pageSize must be 0 for the first page.

D. Because .select('*') must be called after .range().

Solution

1. Step 1: Analyze the range calculation

   For page 1 and pageSize 10, start = 1*10 = 10, end = (1+1)*10 - 1 = 19. This skips rows 0 to 9.

2. Step 2: Understand why no rows appear

   If the table has fewer than 11 rows or you want the first page, you must start at 0. Starting at 10 skips the first 10 rows.

3. Final Answer:

   Because the range starts at 10 instead of 0, skipping the first page. -> Option B

4. Quick Check:

   Page 1 start index = 0, not 10 [OK]

Hint: Page 1 starts at index 0, not page * pageSize [OK]

Common Mistakes:

• Starting range at page * pageSize instead of (page-1)*pageSize
• Misunderstanding zero-based indexing
• Incorrect order of method calls

5. You want to implement infinite scrolling with Supabase pagination. Which approach correctly fetches the next page of 15 items after receiving the first page?

hard

A. Use .range(0, 14) for first page, then .range(15, 29) for second page.

B. Use .range(1, 15) for first page, then .range(16, 30) for second page.

C. Use .range(0, 15) for first page, then .range(15, 30) for second page.

D. Use .range(0, 14) for first page, then .range(14, 29) for second page.

Solution

1. Step 1: Define correct zero-based ranges for pages

   For 15 items per page, first page is indexes 0 to 14 (15 items). Second page starts at 15 and ends at 29.

2. Step 2: Match options with correct ranges

   The option using .range(0, 14) for first page, then .range(15, 29) for second page is correct. It avoids off-by-one errors or overlaps present in the others.

3. Final Answer:

   Use .range(0, 14) for first page, then .range(15, 29) for second page. -> Option A

4. Quick Check:

   Pages must not overlap and cover all items [OK]

Hint: Next page starts at previous end + 1 [OK]

Common Mistakes:

• Overlapping ranges causing duplicate items
• Off-by-one errors in start or end indexes
• Starting second page at wrong index